The present invention relates to the processing and display of digital image sequences and, more particularly, to ameliorating motion sickness induced in viewers of the image sequences.
In a visual display system that depicts a real world motion scene, many people may experience motion sickness, or more precisely, simulator sickness. Individuals experiencing slight levels of simulator sickness may experience some level of positive effects, such as excitement. However, beyond some threshold, the viewer may begin to experience a number of negative effects such as light-headedness, nausea, headache and other undesirable symptoms. It is well understood that providing conflicting or inconsistent psychological cues to a viewer induces this particular type of illness.
In the type of system relevant to the present invention, the display system may provide visual stimulation that provides the perception that a viewer is undergoing motion. However, the individual""s vestibular and/or proprioceptive system may not provide similar stimulation. Instead these systems may indicate the viewer is stationary (or when watching imagery while in a moving vehicle, not consistent with the visual or vestibular system). When conflicting cues are provided to a viewer, the viewer may experience a particular class of simulator sickness. Different people have different susceptibility to this type of sickness and the probability that any individual will experience sickness is dependent upon their susceptibility to this type of sickness and the strength of the visual stimulus.
Individual sensitivity to motion sickness varies quite dramatically. Among the known variables which effect sensitivity to motion sickness are:
Age: younger individuals are generally more susceptible than older individuals
Sex: females are generally more susceptible than males
Race: individuals of Asian background are more susceptible than Europeans or Africans
Expectations and Previous Experience: individuals who have experienced simulator sickness are more likely to experience it in the future.
The strength of the visual stimulus for producing motion sickness is influenced by a number of factors. First, vection (the visually induced perception of self-motion) almost never occurs for display systems that span only a small proportion of the users"" visual field of view. However, vection is typically thought to be a necessary pre-cursor to this type of sickness. Therefore, the visual stimulus that induces simulator sickness will be stronger for images that are displayed to fill a large proportion of the users"" visual field. Further the strength of the percept will be highly dependent on the region of the image that is undergoing motion. Second, the amount of optical flow (or edges representing motion) will influence the onset of this class of simulator sickness. Images with few edges or little detail are less likely to produce this class of simulator sickness than images with significant texture and numbers of edges. Third, since the vestibular system is most sensitive to changes in acceleration, images which depict changing acceleration are more likely to produce sickness than images depicting a constant velocity. Fourth, if an image sequence is captured in stereo with faithful stereoscopic cues, the system may elucidate stronger vection and be more likely to induce illness. Fifth, the depiction of other conflicting information is also likely to increase the probability of the onset of motion sickness. For example, if the image sequence information portrays the viewer navigating the world in a fixed-wing aircraft, then a portion of the image sequence indicating that the viewer is moving backwards is inconsistent with the users"" frame of reference. Likewise, an automobile that rolls more than 45 degrees without rolling over may also be considered as providing information that is inconsistent with the users""frame of reference. In either of these situations and others that provide conflicting information, the viewer is more likely to experience illness.
There is a need therefore for an improved method of generating a digital image sequence that reduces the degree and incidence of motion sickness in viewers.
A method of generating an immersive digital image sequence capable of providing a perception of self-motion, includes the steps of generating the digital image sequence and adjusting the digital image sequence to control the perception of self-motion, such that the degree of motion sickness induced in a viewer of the digital image sequence is controlled.
The present invention has the advantage that it reduces the degree and incidence of motion sickness in viewers of digital image sequences.